VB.NET - WaitForExit() Runtime Exception Error

[blivori]

Can you kindly tell me why I am getting a runtime exception when trying to run this code?

Sub BtnNowClick(sender As Object, e As EventArgs)
		
		Dim myProcess As New Process
		Dim processFile As String = dlgFolder.SelectedPath
		Dim pyLocationDel As String = Path.Combine(dlgFolder.SelectedPath, "pdfmerge.py")
		
        Directory.SetCurrentDirectory(dlgFolder.SelectedPath)
        
        myProcess.Start(pyLocationDel) 
        myProcess.WaitForExit()     
        System.IO.File.Delete(pyLocationDel)
        
		
	End Sub

Basically, what I want, is to detect for a process to be finished and delete a specific file if the process is finished.

I'm getting this error when trying to execute the code:

System.NullReferenceException: Object reference not set to an instance of an object.
       at lgaPDF.MainForm.BtnNowClick(Object sender, EventArgs e) in C:\Documents and Settings\student3\My Documents\SharpDevelop Projects\lgaPDF\lgaPDF\MainForm.vb:line 184
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
       at lgaPDF.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81

Brian

[lolafuertes]

Maybe you need to change your code like

Dim returnedProcess = myProcess.Start(pyLocationDel) 
        returnedProcess.WaitForExit()

See here for reference
Hope this helps